request help: edit request body

[yyl-code]

Issue description

Does the golang plugin support modifying the request body?

Environment

• APISIX Go Plugin Runner's version:
• APISIX version:
• Go version:
• OS (cmd: uname -a):

[soulbird]

Not yet supported

[hongdingyi]

........

[hongdingyi]

i want change request body

[thinkdb1]

我试着修改了几个文件，发现可以修改request body值了，先发你先参考看看

apisix-core-with-plugin/internal/http/request.go中
1.加入

func (r *Request) SetBody(b []byte) {
	r.body = b
}

2.在(r *Request) FetchChanges(id uint32, builder *flatbuffers.Builder)中把

if r.path == nil && r.hdr == nil && r.args == nil && r.respHdr == nil {
		return false
	}

改为

if r.path == nil && r.hdr == nil && r.args == nil && r.respHdr == nil && r.body == nil {
		return false
	}

3.在(r *Request) FetchChanges(id uint32, builder *flatbuffers.Builder)中在

if r.path != nil {
		path = builder.CreateByteString(r.path)
	}

后加入

if r.body != nil {
		body = builder.CreateByteString(r.body)
	}

4.在(r *Request) FetchChanges(id uint32, builder *flatbuffers.Builder)中把

var path flatbuffers.UOffsetT

改为

var path, body flatbuffers.UOffsetT

5.在(r *Request) FetchChanges(id uint32, builder *flatbuffers.Builder)中在

if path > 0 {
		hrc.RewriteAddPath(builder, path)
	}

后加入

if body > 0 {
		hrc.RewriteAddBody(builder, body)
	}

6.在apisix-core-with-plugin/pkg/http/http.go中的Request interface加入
SetBody([]byte)
7.在go.mod中github.com/api7/ext-plugin-proto改为v0.6.1

在使用时使用r.SetBody([]byte("mytestbody"))并且在apisix的3.6.0版本下使用就可以了，我只是试用成功了，没测试是否还有其他问题

[TomCN0803]

I've started a pull request: #151
Features and modifications includes:

• Update github.com/api7/ext-plugin-proto to v0.6.1
• Add SetBody([]byte) to http.Request
• Add a sample request body rewrite plugin
• Add an e2e test for the sample request body rewrite plugin
• Lint some code and add items (e.g. .vscode, go.work) to .gitignore

[Eslam3bdel3al]

the setBody([]byte) works fine when using only "ext-plugin-pre-req" once using both "ext-plugin-pre-req" and "ext-plugin-post-resp", it doesn't work.

[Eslam3bdel3al]

the setBody([]byte) sets the body correctly.

the issue I faced related to the content-length header, as after setting the new body APISIX seems to send the original content-length to the upstream services when using both "ext-plugin-pre-req" and "ext-plugin-post-resp", and that leads to issues related to body parsing in some of these services (express app in my case).

The issue get fixed by deleting the 'content-length' header after setting the new body so it get calculated again to the new length.
r.SetBody(newbody)
r.Header().Del("content-length")